REGENERATION IN URONYCHIA 



97 



gin. The peristome is a relatively deep, sunken area covered 

 over by a thin ectoplasmic sheath. An undulating membrane 

 endoral membrane £"), which on occasions may be everted, balloon- 

 like to the outside, lies on the left side of the peristome, and a 

 similar, pre-oral, membrane lies on the right (P). A few small 

 cirri are inserted at the base of the undulating membrane and near 

 the mouth, but they are inconspicuous and difficult to see. 



m 



--/-i- P 



Fig. 1 Uronychia transfuga Stein drawn from life for cirri, adoral zone and 

 peristome, from dorsal side. E, endoral membrane; P, preoral membrane;?/;., mi- 

 cronucleus. The lowest macronuclear fragment lies in the dorsal lobe. 



The macronucleus consists of from 10 to 14 large spherical 

 bodies of chromatin, arranged as in the figure to form a broken 

 horse-shoe. One of the masses of chromatin is always in the 

 posterior lobe of the dorsal surface. The micronucleus {m) is single 

 and much smaller than any of the bodies of chromatin of the 

 macronucleus. It usually lies between two of the more posterior 

 masses of macronuclear material. 



Movements. There are two distinct types of movement, one, 

 a steady or uniform movement in the direction of the anterior 



